Incidence and Progression of Diabetic Retinopathy in Urban India: Sankara Nethralaya Diabetic Retinopathy Epidemiology and Molecular Genetics Study, 15yr Follow up.

Purpose: To evaluate the 15 year incidence and progression of Diabetic Retinopathy (DR) and identify risk factors among Indian population.Methods: From a cross-sectional study of 1425 subjects, 911 participants took part in the 4-year follow-up. Out of these 911 participants, 140 returned for the 15-year follow-up, with baseline examinations conducted between 2003 and 2006, and subsequent follow-ups occurring from 2007 to 2011 and the current 15-year follow-up from 2018 to 2021. Of the 140 participants, 112 were eligible for analysis after excluding individuals with ungradable fundus photographs.Results: The 15-year incidence of any diabetic retinopathy (DR) was 5%, with mild NPDR and moderate NPDR at 1.57% and 2.7%, respectively. Proliferative DR was observed in 0.71% of cases, while diabetic macular edema (DME) and sight-threatening diabetic retinopathy (STDR) rates were 0.48% and 1.10%, respectively. Age-standardized rates revealed a significant association with increasing age and incident any DR and STDR. DR progression over 15 years included 7.5% one-step and 1.75% two-step progressions, while regression was limited to 1.75% one-step regression. Multiple logistic regression analyses revealed that baseline duration of diabetes, systolic blood pressure, HbA1c levels, and the presence of anemia influenced the incidence of any DR, DME, and STDR. Smoking and higher HbA1c were identified as risk factors for one-step progression of DR.Conclusion: This study provides crucial insights into the long-term incidence, progression, and regression of DR among individuals with Type 2 diabetes in India.